1. Field of the Invention
The present invention relates to a method of preparation of a laminated iron core of an electric device and more particularly to a method of preparation more effectively utilizing the material of a strip for iron cores.
2. Description of the Prior Art
A laminated iron core of a rotary electric device is formed by laminating a number of iron core plates obtained by stamping a strip for iron cores in a desired shape.
In the conventional preparation method, as shown in FIG. 1, iron core discs (11), having an outer diameter R (&lt;W.sub.1) the same as the outer diameter of a stator laminated iron core, are obtained by stamping the strip for iron cores (1) having a width W.sub.1 at a desired stamping gap d and forming a shaft hole (11a) at the center of each iron core disc (11) in an annular form and further stamping the iron core discs (11) to form rotor or stator slots (not shown) so as to separate them into smaller diameter ring plate and larger diameter ring plate. The smaller diameter ring plates and the larger diameter ring plates are respectively laminated to prepare a rotor laminated iron core (100) and a stator laminated iron core (200) as shown in FIG. 3.
In FIG. 2, iron core discs (21) are obtained by stamping a strip for iron cores (2) having a width W.sub.2 (=k) being smaller than the outer diameter R of the stator laminated iron core and each shaft hole (21a) and the slots (not shown) are formed by the same manner as described hereinabove.
In accordance with the conventional preparation of iron core ring plates for the stator and rotor laminated iron cores by stamping iron core discs obtained by stamping a strip for iron cores in the outer diameter of the stator laminated iron core, excess fragments (12), (22) of the strip for iron cores formed between the stamped iron core discs are wasted without a reuse and accordingly, the efficiency for utilization of the strip for iron cores is disadvantageously inferior.